<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
    <title>ShellCheck: SC2323 – `a[(x)]` is the same as `a[x]`. Prefer not wrapping in additional parentheses.</title>
    <link rel="stylesheet" href="css/bootstrap.min.css" />
  </head>
  <body style="margin-left: auto; margin-right: auto; max-width: 800px">
    <h1>SC2323 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2323">See this page on GitHub</a>
    <p style="display: none"><a href="index.html">Sitemap</a></p>
    <hr />
    <h2
id="ax-is-the-same-as-ax-prefer-not-wrapping-in-additional-parentheses"><code>a[(x)]</code>
is the same as <code>a[x]</code>. Prefer not wrapping in additional
parentheses.</h2>
<p>Similarly <code>$(( (x) ))</code> is the same as
<code>$(( x ))</code>, <code>(( (x) ))</code> is the same as
<code>(( x ))</code>.</p>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2323.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="va">array</span><span class="op">[</span>(x+1)<span class="op">]=</span>val</span>
<span id="cb1-2"><a href="SC2323.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="bu">echo</span> <span class="va">$((</span> (<span class="va">x</span><span class="op">+</span><span class="dv">1</span>) <span class="va">))</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2323.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="va">array</span><span class="op">[</span>x+1<span class="op">]=</span>val</span>
<span id="cb2-2"><a href="SC2323.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="bu">echo</span> <span class="va">$((x</span><span class="op">+</span><span class="dv">1</span><span class="va">))</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>ShellCheck found an entire arithmetic expression wrapped in
parentheses. This does not serve a purpose since the expression is
already clearly delimited by the construct it's in, such as
<code>array[..]=</code> or <code>$((..))</code> in the example.</p>
<p>Note: ShellCheck does <em>not</em> warn about redundant parentheses
in subexpressions, such as <code>(a*b)+c</code>. Feel free to use
parentheses to clarify the order of operations any way you'd like.
ShellCheck only emits this suggestion when the <em>entire</em>
expression is wrapped <em>twice</em>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>If you prefer having an extra layer of parentheses for stylistic
reasons, you can <a href="ignore.html">ignore</a> this message.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
    <hr />
    <p style='font-size: 80%'><a href="../index.html">ShellCheck</a> is a static analysis tool for shell scripts. This page is part of its documentation.</p>
  </body>
</html>


